A. Field of the Invention
The present invention relates to a control system for a programmable control device (PC) which executes a user program cyclically, and more specifically, to a control system for a PC device permitting output signal conditions in a stop mode to be arbitrarily programmed by a user program.
b. Description of Related Art
The operation conditions of a PC device include an operation mode and a stop mode. Usually, all of the output signals are compulsorily turned off in the stop mode. Sometimes, however, an output signal must remain in the same condition in the operation mode, depending on the character of the signal, when the PC device is in the stop mode. For example, a signal effecting a mechanical operation when in an "ON" state must be turned "OFF" in the stop mode. On the other hand, preferably an output signal controlling a clamp mechanism and the like is kept in the "ON" state in the stop mode.
In a known PC device control system, parameters are provided by which all output signals or a part of thereof can be turned "OFF" or kept in their previous state, in a stop mode. In such a system the above conditions are set by using a plurality of parameters. However, an increase in the number of signals means that the number of parameters to be set must be increased, and thus it becomes difficult to set a parameter for each signal. Further, to ensure a required operation of the PC device, the parameters must be correctly set, in addition to the creation of a program, by the user.